You might have noticed two terminals, one at each end of the battery. One marked positive and other marked negative. In order to understand the working of a battery, let us first understand the terms ions, electrodes and electrolyte.
Electrodes are conductors that pass current from one medium to another. They could be a rod, a wire or even a plate. An ‘ion’ is an atom or molecule that doesn’t have equal number of protons and electrons. It is said to be electrically charged. An electrolyte is a solution that contains free ions which makes it electrically conductive. The positive ions in the electrolyte are called cations and negative ions are called anions.
To utilize the energy produced by the battery, we connect a load like a ‘bulb’ to the terminals of the battery. The internal components of a battery are enclosed within a metal or plastic case. There are two electrodes connected in series by a conductive electrolyte in the casing. The electrode connected to the positive terminal is called cathode and to the negative terminal is called anode. Both do not touch each other and are separated via a separator in the electrolyte medium.
When the battery is put to use, two chemical reactions occur between anode and cathode placed inside the electrolyte medium. One is the process of ‘loss of electrons’ called ‘oxidation’ and other process involves ‘gain of electrons’ called ‘reduction’. The anode experiences oxidation reaction and cathode experiences reduction reaction. Anode creates electrons that are absorbed by cathode. The electrolyte allows the flow of electrons between anode and cathode resulting in current flow. The battery can produce current until the electrodes run out of the substance necessary for Redox (oxidation-reduction) reactions to occur.
Normal alkaline batteries used for flashlight are single-use or primary cells of 1.5v. Secondary batteries can be discharged and recharged. A Car battery is a 12-volt battery whose terminals are situated next to each other on the top of the unit. When a wire is connected between the positive and negative terminal of a battery, electrons start flowing from the negative side to positive side. This is quite dangerous and will wear out the battery quickly.
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